Question: Solve for $x$ and $y$ using substitution. ${2x-3y = -9}$ ${y = 2x-1}$
Answer: Since $y$ has already been solved for, substitute $2x-1$ for $y$ in the first equation. ${2x - 3}{(2x-1)}{= -9}$ Simplify and solve for $x$ $2x-6x + 3 = -9$ $-4x+3 = -9$ $-4x+3{-3} = -9{-3}$ $-4x = -12$ $\dfrac{-4x}{{-4}} = \dfrac{-12}{{-4}}$ ${x = 3}$ Now that you know ${x = 3}$ , plug it back into $\thinspace {y = 2x-1}\thinspace$ to find $y$ ${y = 2}{(3)}{ - 1}$ $y = 6 - 1$ $y = 5$ You can also plug ${x = 3}$ into $\thinspace {2x-3y = -9}\thinspace$ and get the same answer for $y$ : ${2}{(3)}{ - 3y = -9}$ ${y = 5}$